Abstract

MIRANDA, M.; RODRIGUES, L.  and  BRITO, P.. Corrosion study of the outlet pipe of an heat exchanger in an industrial co-generation system. Corros. Prot. Mater. [online]. 2012, vol.31, n.3-4, pp.71-75. ISSN 2182-6587.

Heat and power co-generation has been used in industry as a smart way to promote energy efficiency as well as to reduce the equivalent amount of pollutants emissions resulting from the burning of fossil fuels. Heat exchangers are one of the most used devices to perform the needed heat transference between the involved fluids, in particular serpentine and shell and tubes heat exchangers. Materials used in the fabrication of this type of equipments are steels of different compositions that warranty variable lifetimes depending on its corrosion behavior in the fluid used to perform the heat transference, the so called “thermofluid”. However, operation with moving hot aqueous fluids poses additional stress from the point of view of corrosion degradation of these materials, causing frequent spot failures in the most susceptible regions, such as tubing knees, tanks and other equipments inlet and outlet. This work presents the results of a corrosion failure analysis observed in a condensate line, downstream to a heat exchanger of a co-generation system in a factory in Portalegre region, Portugal. Results show that the failure, that presents in the form of grooves in the inner hall of the tube and perforation in some places, is most probably due to the combined chemical (corrosion) and mechanical (erosion) interaction of tubing material with the degraded thermofluid that circulate inside it. In fact, the degradation of some of the termofluid components renders it more aggressive towards the tubing material. These conclusions were withdrawn from potentiometric and potentiodynamic electrochemical tests through the determination of corrosion rates of probe of the tubing material at room temperature and at heat-exchanger operation temperature (around 63 ºC).

Keywords : Co-generation; Corrosion; Thermofluid; Heat-Exchanger.

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